1. Field of the Invention
This invention relates to a flash modulation control apparatus in a camera of the TTL automatic light modulation type, and particularly an apparatus for setting a photographing mode in conformity with an object, and effecting light modulation control in accordance with the photometry area and light amount level of the object field optimal to the photographing mode.
2. Related Background Art
There is known a flash modulation control apparatus in a camera of the TTL automatic light modulation type which effects light modulation so that after the light emission of a flash device is started during flash photographing, the light emission of the flash device may be stopped when the amount of reflected light from an object reaches a predetermined light amount level, whereby proper exposure may be obtained.
The photometry area of the apparatus of this kind is substantially the whole of the photographing image field, or a relatively wide range including the center of the image field. Also, the light amount level which determines the timing of the stoppage of the light emission is determined on the basis of light reflected at a predetermined proportion relative to a certain predetermined amount of light emitted. For example, an object having a certain predetermined reflectivity (average reflectivity) is disposed in opposed relationship with the flash device so as to cover an area for effecting photometry, and a TTL light amount level is determined on the basis of such a relation between time and light amount that the object is photographed at proper exposure during flash emission.
However, the reflectivity of the object field during ordinary flash photographing is not uniform and therefore, when flash photographing is effected by the use of a conventional device, there arises the problem that exposure becomes over or under depending on the object.
For example, if the number of persons or bodies which are main objects increases or decreases, the area that main objects lying at the same distance occupy for the photometry area in the photographing image field varies and the amounts of reflected light from these main objects vary. However, the amount of light emitted from the flash device is controlled on the basis of a TTL light amount level determined with an object of the average reflectivity supposed and therefore, if the number of main objects increases, the amount of reflected light increases and light emission is stopped early and thus, the exposure for the main objects becomes under. If conversely, the number of main objects decreases, the amount of reflected light decreases and the time when light emission is stopped becomes late, and the exposure for the main objects becomes over. A similar phenomenon occurs when lenses of different focal lengths are used. That is, if the focal length becomes smaller (if a wide angle lens is used), the size of the main object in the photographing image field becomes smaller and the background range photographed becomes wider and therefore, the amount of reflected light from the main object decreases and the time when light emission is stopped becomes late, and the exposure for the main object becomes over. On the other hand, if the focal length becomes greater (if a telephoto lens is used), the size of the main object in the photographing image field becomes larger and the background range photographed becomes narrower and therefore, the amount of reflected light from the main object increases and the time when light emission is stopped becomes early, and the exposure for the main object becomes under.
Also, in the prior-art apparatus, reflected light from an object is metered in the whole of the photographing image field or a wide range including the central portion of the image field, and this also leads to the problem that proper exposure is not obtained for a main object when the main object occupies a relatively narrow range in the photographing image field or when the main object is not at the center of the image field.